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题如图1,在ΔABC中,AD是∠BAC的角平分线,若AB+BD=25,AC-CD=4,求AD的长.这道看上去很一般的竞赛训练题目,经我仔细
The problem is shown in Figure 1. In ΔABC, AD is the angle bisector of BAC. If AB+BD=25 and AC-CD=4, the length of AD will be long. This is a very general race training topic.